The existence of a dietary requirement for fatty acids of the omega-3 or Alpha-linolenic acid family has been an unresolved issue in human nutrition. Like the omega-6 or linoleic acid family, omega-3 fatty acids cannot be synthesized by animals. The high content of these fatty acids, particularly docosahexaenoic acid (22:6 omega-3 or DHA), in the phospholipids of the retina and cerebral cortex suggests an important role in the function of neuronal and photoreceptor membranes. We have now produced omega-3 fatty acid deficiency in rhesus monkeys by dietary deprivation throughout gestation and infancy. The deficiency state is characterized by both biochemical and functional changes. The plasma and tissues exhibit reduced levels of omega-3 fatty acids from birth to two years of age. Levels of DHA are greatly reduced in brain and retina. Visual defects and abnormal electroretinograms occur in deficient animals. We now propose to continue studies of existing omega-3 fatty acid deficient monkeys to investigate these questions: 1. Does the deficient state produce increasing manifestations of visual loss with increased age? 2. Do juvenile deficient animals show impairments in tests of complex learning? 3. Will the correction of the omega-3 fatty acid deficient diet with DHA or linolenic acid correct both the functional and biochemical abnormalities of deficient monkeys? In addition, we propose to begin breeding a new group of deficient adult females in order to investigate the following questions: 4. How rapidly will infants deficient at birth regain normal levels of DHA after dietary repletion with dietary omega-3 fatty acids (DHA or linolenic acid)? Will visual loss then be avoided? These studies will help determine the nutritional needs of primates for omega-3 fatty acids during different stages of development. This work has implications for the optimum diet of pregnant and lactating women, human infants, and perhaps of older humans. Finally, these studies will provide information about the biochemistry of the developing primate brain.